Agonistic behavior governs the settlement of conflicts among conspecifics for limiting resources. Sex steroids play a critical role in the regulation of agonistic behavior which in turn may produce modulations in hormone titres. In this study we analyzed the association of androgens and estrogens with agonistic behavior in the annual fish Austrolebias reicherti. This native species inhabits temporary ponds that dry out completely during summer, having one of the shortest lifespans among vertebrates. They are highly sexually dimorphic and have a single breeding season during which they reproduce continuously. Here we measured plasma levels of 11-ketotestosterone (11KT) and 17β-estradiol (E2) in adult males after the resolution of a social conflict and assessed the role of the aromatase conversion of testosterone (T) to E2 in male aggression. Winners had higher levels of 11KT than losers yet; winner 11KT levels did not differ from those of males not exposed to a social challenge. E2 levels did not show differences among winners, losers or control males. However, fights under the aromatase inhibitor Fadrozole were overall less aggressive than control fights. Our results suggest an androgen response to losing a conflict and that the conversion of T to E2 is involved in the regulation of aggressive behavior. Annual fish extreme life history may give new insights on hormone-behavior interactions.
Keywords: 11-Ketotestosterone; Androgen response; Aromatase; Estradiol; Killifish; Male aggression.
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